We present a general analysis of thickness errors in multilayers using the classical existing methods, and adding a complimentary tool based on admittance perturbed circumferences that allow us to obtain a deeper insight into the spectral performance sensitivity due to each layer composing the system. An analysis of the standard deviation of reflectance based on perturbing the system with statistical thickness errors is considered. The proposed method represents a useful tool to study the sensitivity of any multilayer to determine the manufacturing feasibility in the design stage that can save a number of trial deposition experiments while setting up the manufacturing process of a given system. This fact is demonstrated by considering different classical systems with highly stable and instable spectral regions.
We investigate the spectral response of capacitive sensors with 28 μm thick Polyvinylidene Fluoride (PVDF) films operating in the piezoelectric mode. We present spectra of signals obtained from laser-induced photoacoustic emissions in several materials. We examine the sensor response to direct laser pulses and to ultrasonic signals generated by laser pulses interacting with polyvinyl alcohol (PVA) phantoms, neoprene slabs and a composite of PVA phantom with a hidden slab of neoprene. We exhibit the sensor's sensitivity to the phantom thickness, affecting the amplitude and bandwidth of the ultrasonic output signal. The sensors fabricated and tested under water achieved an operational frequency bandwidth ranging from 1 to 50 MHz.